Update ioutil library references to os and io respectively for API and Plugins package (#16330)

No user facing changes so I assume no change log is required

plugins/drivers/testutils/exec_testing.go

@@ -4,7 +4,6 @@ import (
 	"context"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"os"
 	"reflect"
 	"regexp"
@@ -176,7 +175,7 @@ func TestExecFSIsolation(t *testing.T, driver *DriverHarness, taskID string) {
 		t.Logf("created file in task: %v", tempfile)
 
 		// read from host
-		b, err := ioutil.ReadFile(tempfile)
+		b, err := os.ReadFile(tempfile)
 		if !isolated {
 			require.NoError(t, err)
 			require.Equal(t, text, strings.TrimSpace(string(b)))

plugins/drivers/testutils/testing.go

@@ -3,7 +3,6 @@ package testutils
 import (
 	"context"
 	"fmt"
-	"io/ioutil"
 	"os"
 	"path/filepath"
 	"runtime"
@@ -116,7 +115,7 @@ func (h *DriverHarness) cleanupCgroup() {
 // A cleanup func is returned and should be deferred so as to not leak dirs
 // between tests.
 func (h *DriverHarness) MkAllocDir(t *drivers.TaskConfig, enableLogs bool) func() {
-	dir, err := ioutil.TempDir("", "nomad_driver_harness-")
+	dir, err := os.MkdirTemp("", "nomad_driver_harness-")
 	require.NoError(h.t, err)
 
 	allocDir := allocdir.NewAllocDir(h.logger, dir, t.AllocID)

plugins/shared/cmd/launcher/command/device.go

@@ -4,7 +4,6 @@ import (
 	"context"
 	"errors"
 	"fmt"
-	"io/ioutil"
 	"os"
 	"os/exec"
 	"strings"
@@ -95,7 +94,7 @@ func (c *Device) Run(args []string) int {
 	var config []byte
 	if numArgs == 2 {
 		var err error
-		config, err = ioutil.ReadFile(args[1])
+		config, err = os.ReadFile(args[1])
 		if err != nil {
 			c.logger.Error("failed to read config file", "error", err)
 			return 1